1. Field of the Invention
The present invention relates to a cooking device such as an electronic oven for heating an object to be heated by emitting microwaves into a heating chamber and, more particularly, to a cooking device for uniformly heating the object to be heated by uniformly emitting the microwaves into the heating chamber.
2. Description of the Background Art
Hitherto, an electronic oven A shown in FIGS. 6 and 7 is known as an example of a cooking device. FIG. 6 is a front sectional view of electronic oven A and FIG. 7 is a sectional view taken along line B—B of FIG. 6. Electronic oven A includes: a body 1; a heating chamber 2 housing objects 13-1 to 13-3 to be heated which are provided in the body 1; a cooking plate 3 made of glass, ceramics, or the like provided at a predetermined interval from the bottom face of heating chamber 2 and parallel with the bottom face; a microwave generator 4 having a magnetron provided on the outside of the body 1 and close to the body 1; a waveguide tube 5 for guiding microwaves generated from microwave generator 4 into heating chamber 2; a communication hole 10 through which waveguide tube 5 and heating chamber 2 communicate with each other; a coupling antenna 11 disposed coaxially to the center axis of communication hole 10; a flat antenna 12 made from a disc-shaped metal plate connected to the top portion on the heating chamber side of coupling antenna 11 and having plural openings; and a driving device 6 for rotating coupling antenna 11.
When a heating start switch is turned on by an operating unit (not shown) provided for the conventionally known electronic oven A, microwaves of 2,450 MHz generated by microwave generator 4 are emitted toward waveguide tube 5. The emitted microwaves are guided into heating chamber 2 via waveguide tube 5 and communication hole 10. Part of the microwaves guided into heating chamber 2 passes through a waveguide path R formed by flat antenna 12 and a bottom face 2a of heating chamber 2, propagates radially along the bottom face so as to be apart from communication hole 10 and, in a region after the outer peripheral portion of flat antenna 12, is guided toward the inside of heating chamber 2. Part of the microwaves guided from communication hole 10 into heating chamber 2 passes through plural openings 14 (see FIG. 7) formed in flat antenna 12 to above of flat antenna 12.
The microwaves are guided into heating chamber 2 and propagate in a wide range in such a manner, thereby irradiating objects 13-1 to 13-3 to be heated which are mounted on cooking plate 3 with microwaves and heating objects 13-1 to 13-3 to be heated.
Japanese Laid-Open Patent Publication No. 2002-151248 discloses a high-frequency heating device having a structure similar to that of electronic oven A.